Mullite is a compound of aluminum oxide and silicon oxide in a proportion (Al.sub.2 O.sub.3 : SiO.sub.2) of 3:2. Because of its good mechanical properties, it can be used at high temperatures in high-performance ceramics.
The production of highly disperse mixed oxides is described in German Patent DE 952 891 and German Patent DE 29 31 585. The production of a mullite-aluminum oxide sintered compact is described in Published German Patent Application DE 38 35 966.
It is known that the oxides of silicon dioxide and aluminum dioxide can be produced both individually and conjointly by allowing the chlorides to react in an evaporated state in an oxyhydrogen flame with the water produced in this flame, during which fine oxide is formed (See Published German Patent Application DE-A 952 891).